Semiparametric estimation of the transformation model by leveraging external aggregate data in the presence of population heterogeneity

Leveraging information in aggregate data from external sources to improve estimation efficiency and prediction accuracy with smaller scale studies has drawn a great deal of attention in recent years. Yet, conventional methods often either ignore uncertainty in the external information or fail to account for the heterogeneity between internal and external studies. This article proposes an empirical likelihood-based framework to improve the estimation of the semiparametric transformation models by incorporating information about the t-year subgroup survival probability from external sources. The proposed estimation procedure incorporates an additional likelihood component to account for uncertainty in the external information and employs a density ratio model to characterize population heterogeneity. We establish the consistency and asymptotic normality of the proposed estimator and show that it is more efficient than the conventional pseudopartial likelihood estimator without combining information. Simulation studies show that the proposed estimator yields little bias and outperforms the conventional approach even in the presence of information uncertainty and heterogeneity. The proposed methodologies are illustrated with an analysis of a pancreatic cancer study.     

A major difference between the divergence patterns within the lines-1 families in mice and voles

L1 retroposons are represented in mice by subfamilies of interspersed sequences of varied abundance. Previous analyses have indicated that subfamilies are generated by duplicative transposition of a small number of members of the L1 family, the progeny of which then become a major component of the murine L1 population, and are not due to any active processes generating homology within preexisting groups of elements in a particular species. In mice, more than a third of the L1 elements belong to a clade that became active approximately 5 Mya and whose elements are > or = 95% identical. We have collected sequence information from 13 L1 elements isolated from two species of voles (Rodentia: Microtinae: Microtus and Arvicola) and have found that divergence within the vole L1 population is quite different from that in mice, in that there is no abundant subfamily of homologous elements. Individual L1 elements from voles are very divergent from one another and belong to a clade that began a period of elevated duplicative transposition approximately 13 Mya. Sequence analyses of portions of these divergent L1 elements (approximately 250 bp each) gave no evidence for concerted evolution having acted on the vole L1 elements since the split of the two vole lineages approximately 3.5 Mya; that is, the observed interspecific divergence (6.7%-24.7%) is not larger than the intraspecific divergence (7.9%-27.2%), and phylogenetic analyses showed no clustering into Arvicola and Microtus clades.      

PDGF-AA activates AKT and ERK signaling for testicular interstitial Leydig cell growth via primary cilia

Testes control the development of male reproductive system. The testicular interstitial Leydig cells (Leydig cells) synthesize testosterone for promoting spermatogenesis and secondary sexual characteristics. Type A platelet-derived growth factor (PDGF-AA) is one of the most important growth factors in regulating Leydig cell growth and function. Knockout of PDGF-AA or its congenital receptor PDGFR-α leads to poor testicular development caused by reducing Leydig cell numbers, supporting PDGF-AA/PDGFR-α signaling regulates Leydig cell development. Primary cilium is a cellular antenna that functions as an integrative platform to transduce extracellular signaling for proper development and differentiation. Several receptors including PDGFR-α are observed on primary cilia for initiating signaling cascades in distinct cell types. Here we showed that PDGF-AA/PDGFR-α signaling promoted Leydig cells growth, migration, and invasion via primary cilia. Upon PDGF-AA treatment, AKT and ERK signaling were activated to regulate these cellular events. Interestingly, active AKT and ERK were detected around the base of primary cilia. Depletion of ciliary genes (IFT88 and CEP164) alleviated PDGF-AA-activated AKT and ERK, thus reducing Leydig cell growth, migration, and invasion. Thus, our study not only reveals the function of PDGF-AA/PDGFR-α signaling in maintaining testicular physiology but also uncovers the role of primary cilium and downstream signaling in regulating Leydig cell development.     

视力与视觉诱发电位的相关分析

对104例病人的图形翻转VEP的瞬态波形各参数,以及9例正常或近视学生的稳态曲线功率谱与视力之间的关系进行了多元相关统计分析,旨在探讨VEP的哪些参数可客观地评估视力.结果表明,瞬态VEP的波形参数中以13’格诱发的N_1P_1、P_1N_2的峰峰值及P_(100)潜伏期与视力的相关系数最大,故认为,分析视力时以平均P_(100)波的波幅值和P_(100)波潜伏期作指标较为灵敏;而稳态、VEP能谱曲线则显示,视力与平均相叶能谱或刺激频率点的能谱相关性较大,与二次谐波的相关性则小.     

Further characterization of nociception-related and arterial pressure-related neuronal responses in the nucleus reticularis gigantocellularis of the rat

The present study was undertaken to further characterize the nucleus reticularis gigantocellularis (NRGC) of the medulla oblongata in the central processing of nociceptive and cardiovascular signals, and its modulation by metenkephalin. In Sprague-Dawley rats anesthetized with pentobarbital sodium, we found that all 125 spontaneously active NRGC neurons that responded to noxious stimuli (tail clamp) also exhibited arterial pressure-relatedness. Forty neurons additionally manifested cardiac periodicity that persisted even during nociceptive responses. While maintaining their cardiovascular responsive characteristics, the nociception-related NRGC neuronal activity was blocked, naloxone-reversibly (0.5 mg/kg, i.v.), by morphine (5 mg/kg, i.v.). Microiontophoretically applied met-enkephalin suppressed the responsiveness of NRGC neurons to individually delivered tail clamp or transient hypertension induced by phenylephrine (5 µg/kg, i.v.). Interestingly, in NRGC neurons that manifested both nociception and arterial pressure relatedness, the preferential reduction in the response to noxious stimuli upon simultaneous elevation in systemic arterial pressure was reversed to one that favored nociception in the presence of met-enkephalin. All actions of met-enkephalin were discernibly blocked by the opioid receptor antagonist, naloxone. Our results suggest that individual NRGC neurons may participate in the processing of both nociceptive and cardiovascular information, or in the coordination of the necessary circulatory supports during nociception. In addition, neuropeptides such as met-enkephalin may exert differential modulation on neuronal responsiveness according to the prevailing physiologic status of the animal. They also showed that NRGC may be a central integrator for pain and cardiovascular-related functions.     

Assessing post-induction cellular response in a recombinant E. coli lactose-inducible system by monitoring β-galactosidase levels

Summary A synthetic lactose-inducible promoter was chosen to study host cell responses to the over-expression of heterologous genes. Fermentations were conducted to compare the effect of induction strategies on the synthesis of -galactosidase versus the production of recombinant protein. The levels of lactose, IPTG and glucose during induction were manipulated to adjust the utilization of lactose as the inducer and/or the carbon source. In addition, the involvement of the gal operon in lactose metabolism was also explored in order to optimize lactose transport and utilization during induction.     

Improvement of Escherichia coli microaerobic oxygen metabolism by Vitreoscilla hemoglobin: New insights from NAD(P)H fluorescence and culture redox potential

On-line NAD(P)H fluorescence and culture redox potential (CRP) measurements were utilized to investigate the role of Vitreoscilla hemoglobin (VHb) in perturbing oxygen metabolism of microaerobic Escherichia coli Batch cultures of a VHb-synthesizing E. coli strain and the iso-genic control under fully aerated conditions were subject to several high/low oxygen transitions, and the NAD(P)H fluorescence and CRP were monitored during these passages. The presence of VHb decreased the rate of net NAD(P)H generation by 2.4-fold under diminishing oxygen tension. In the absence of aeration, the strain producing VHb maintained a steady NAD(P)H level 1.8-fold less than that of the control, indicating that the presence of VHb keeps E. coli in a more oxidized state under oxygen-limited conditions. Estimated from CRP, the oxygen uptake rates near anoxia were 25% higher for cells with VHb than those without. These results suggest that VHb-expressing cells have a higher microaerobic electron transport chain turnover rate. To examine how NAD(P)H utilization of VHb-expressing cells responds to rapidly changing oxygen tension, which is common in large-scale fermentations, we pulsed air intermittently into a cell suspension and recorded the fluorescence response to the imposed dissolved oxygen (DO) fluctuation. Relative to the control, cells containing VHb had a sluggish fluorescence response to sudden changes of oxygen tension, suggesting that VHb buffers intracellular redox perturbations caused by extracellular DO fluctuations.(c) John Wiley & Sons, Inc.